Variable-resistance medium for telephones



1 UNITED STATES PATENT ()FFICE.

WILLIAM JACQUES, OF NEWTON, ASSIGNOR TO .THE AMERICAN BELL microphonicsilicon and .in the TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

VARIABLE-RESlSTANCE MEDIUM FOR TELEPHONQES.

SPECIFICATION forn ling part of Letters Patent No. 524,173, dated.August 7, 1894.

Application filed May 14, 1894:. Serial No. 511,240. 1 (N0 specimens.)

To all whom, it may concern.-

Be it known that 1, WILLIAM W. JAC ES, of Newton, in the State ofMassachusetts, have invented a new and useful Variable-Resistance Mediumfor Battery-Telephone Transmitters, of which the following'is aspecifi-- cation.

The invention consists in an electric and process by which the same isproduced.

The said process consists in reducing a. salt of silicon by heatingitwith sodium or potassium and again heating the product to a white a heatin the absence of air.

I mix fiuorsilicate of potassium with metallicsodium or potassium inproper proportions to reducethe flnorsilicate of potassium. Themixture.is then heated to redness in a closed iron retort. After the reactionhas taken place the product is treated first with cold andcthen with hotwater and filtered. The residue,

consisting of amorphous silicon, is then-heated to a reddish white heatin a closed vessel from which the air is excluded. The product thusobtained is a granular electric and microphonic silicon suitable to beused as av variable resistance medium between electrodes in batterytelephones of the'Hunnings or granular type.

' I claiml. A microphonic element composed of silicon havingelectricalconductivity.

. 2. The herein described process of produc- Witnesses:

WILLIA W. SWAN, WILLIAM SULLIVAN.

